Over the last year, this lab has been engaged in three main projects. (A) Mapping of human genes with the Mouse X human hybrid. We are primarily concerned with the cystic fibrosis gene and the development of new stains to reveal other linkage relationships. (B) Biochemically selectible functions in Differentiated Cells. We are now engaged in developing selection systems with our prime effort devoted to liver specific functions. (C) Cell Attachment Factor. We previously identified a serum protein that is required for mammalian cell attachment to collagen. The cell attachment protein requires Ca ions or Mg ions for activity. Recently, we have shown that ATP energy is required from cells to attach to collagen.